I grew up in an all-white town in Indiana. I still am embarrassed by a racist remark I made 51 years ago. It was part of the language and I didn’t even realize what I said until later.
Racism, sexism, and other prejudices are built into the language and culture. It takes years, decades and centuries to change them significantly. Unless a person is open to change and has thought about it, change will not happen. I doubt that Mrs. Martignon was capable of changing. She may have even thought about it, but was unable to get past years of training.
I started thinking about it after another incident, positive instead of negative, in 1964 and have many examples of non-racist behavior, but cannot guarantee that something isn’t deeply buried that could still rear its ugly head.
It appears from this article that it is a world-wide problem and not just in the US like we are taught.